J Inorg Organomet Polym (2011) 21:171–174 DOI 10.1007/s10904-010-9443-9
COMMUNICATION
Direct Synthesis of Cd3OSO4 Nano-particles From a New Three-dimensional Cadmium(II) Coordination Polymer Precursor Gholam Hossein Shahverdizadeh • Shahla Masoudian • Ali Akbar Soudi • Fahime Bigdeli • Hassan Hosseini Monfared Ali Morsali • Hamid Reza Khavasi
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Received: 10 May 2010 / Accepted: 29 November 2010 / Published online: 23 December 2010 Ó Springer Science+Business Media, LLC 2010
Abstract A new three-dimensional Cd(II) coordination polymer, {[Cd3(3-pyc)4(NCS)2(H2O)4]2H2O}n (1); 3-Hpyc = 3-pyridinecarboxylic acid, was prepared and characterized by elemental analyses and IR spectroscopy. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The structural determination shows that the compound is a new 3D coordination polymer has different environments containing CdO5NS and CdO2N4 units. This polymeric precursor has been used in the preparation of Cd3OSO4 nanoparticles by thermolysis in oleic acid. The new nano-structure of Cd3OSO4 was characterized by scanning electron microscopy and X-ray powder diffraction. This study demonstrates that coordination polymers may be suitable precursors to the preparation of desirable nanoscale materials. Keywords Crystal structure Thermal properties Nano-materials Cadmium(II) G. H. Shahverdizadeh (&) Department of Applied Chemistry, Research Laboratory, Islamic Azad University, Tabriz Branch, Tabriz, Iran e-mail:
[email protected] S. Masoudian A. A. Soudi H. H. Monfared Department of Chemistry, Zanjan University, Zanjan, Iran F. Bigdeli Department of Chemistry, Payame Noor University, Abhar, Iran A. Morsali (&) Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14155-4838, Tehran, Iran e-mail:
[email protected] H. R. Khavasi Department of Chemistry, Shahid Beheshti University, Evin, P.O. Box 19839-63113, Tehran, Iran
1 Introduction The self-assembly of coordination polymers (supramolecular molecules) with novel structures and properties has attracted considerable interest by chemists due to their diverse topologies and potential applications in smart optoelectronic, magnetic, microporous and biomimetic materials [1–23]. Considerable effort has been dedicated to the controlled synthesis of nanoscale particles of metals, oxides, sulfides, and ceramic materials; however, little attention has been focused on nanoparticles of supramolecular compounds such as coordination polymers. Metal oxides display appealing electronic, optical, thermo-electronic and photo-electronic properties. Cadmium compounds, in particular, are semiconductors with a well-established direct band gap. Such materials have applications in solar cells, as transparent electrodes, as photodiodes and in sensors [24–31]. The nanoparticles of Cd3OSO4, if used for such applications, are expected to play a major role in improving optical and electrical properties. This article focuses attention on the simple preparation of a new Cd(II) coordination polymer, [Cd3(3-pyc)4(NCS)2 (H2O)4]2H2O}n (1), where 3-Hpyc is 3-pyridinecarboxylic, and its use for the preparation of Cd3OSO4 nanoparticles using oleic acid as a surfactant.
2 Experimental 2.1 Materials and Physical Techniques All reagents and solvents for the synthesis and analysis were commercially available (Merck) and used as received. X-ray powder diffraction (XRD) measurements were performed using an X’pert diffractometer (Philips Company)
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with monochromatized Cu Ka radiation. The samples were characterized by scanning electron microscopy (SEM) (Philips XL 30) with gold coating. IR spectra were recorded on a SHIMADZU-IR460 spectrometer in a KBr matrix. Crystallographic measurements of compound 1 were made at 120(2) K using a Stoe-IPDS-2 diffractometer equipped with a graphite monochromated Mo Ka radiation ˚ ). (k = 0.71073 A 2.2 Preparation of {[Cd3(3-pyc)4 (NCS)2(H2O)4]2H2O}n (1) Compound 1 was prepared using the branched tube method [32]: 3-pyridinecarboxylic (0.123 g, 1 mmol), sodium hydroxide (0.04 g, 1 mmol), potassium thiocyanate (0.98 g, 1 mmol) and Cd(II) acetate dihydrate (0.266 g, 1 mmol) were placed in the arm to be heated. Water was carefully added to fill both arms, and then the arm to be heated was placed in a bath at 60 °C. After 6 days, colourless crystals were deposited in the cooler arm, which were filtered, washed with water and air dried (0.185 g, yield 69%), m.p. [300 °C. Elemental analysis (%): Calculated for C26H28Cd3N6O14S2; C, 29.76; H, 2.69; N, 8.01; Found C, 29.72; H, 2.71; N, 8.10%. IR: selected bands cm-1 (intensity); 753 (m), 1409 (s), 1559 (s), 1607 (vs), 2000 (m), 3393 (br).
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EtOH and dried under nitrogen [yield, analytical properties and characterization].
3 Results and Discussion Reaction between 3-pyridinecarboxylic (3-Hpyc) with a mixture of Cd(II) acetate, sodium hydroxide and potassium thiocyanate leads to the formation of a new 3D Cd(II) coordination polymer, {[Cd3(3-pyc)4(NCS)2(H2O)4]2H2O}n (1). The crystal data for 1 indicate a monoclinic, space group P21/n, ˚, b = a = 7.9474(7), b = 15.7511(10), c = 14.1292(12) A ˚ 3, Z = 2, T = 120(2) K. The IR 95.049(7)°, V = 1761.8(2) A absorption bands in the frequency range 1405–1607 cm-1 correspond to vibrations of the pyridine rings. m(COO) vibrations are found at ca. 1409 and 1607 cm-1. The D (tas-tsym) values indicate that the carboxylate anions coordinate to the Cd(II) center in a bridging mode. The broad band at 3,300 cm-1 shows the existence of water in 1 [33]. Single-crystal X-ray diffraction analysis of 1 reveals that there are two Cd(II)
2.3 Preparation of Cd3OSO4 Nanoparticles A small amount of 1 (0.1049 g, 0.1 mmol) was dissolved in oleic acid (0.2 ml) and the solution was then heated to 280 °C and then 300 °C for 2 h. A dark green precipitate was observed in a brown solution. A small amount of toluene and a large excess of MeOH were added to the reaction solution and Cd3OSO4 nanoparticles were separated by centrifugation. The dark solid was washed with Fig. 1 Molecular view of the repeating unit in {[Cd3(3-pyc)4 (NCS)2(H2O)4]2H2O}n (1)
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Fig. 2 Depiction of 3D coordination polymer in compound {[Cd3 (3-pyc)4(NCS)2(H2O)4]2H2O}n (1)
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Fig. 3 SEM photographs of Cd3OSO4 nanoparticles produced by thermolysis of 1 at 280 °C (top) and 300 °C (bottom)
ions with different environments, i.e. CdO5NS and CdO2N4. The Cd(II) atoms are coordinated by water molecules, 3-pyridinecarboxylate and thiocyanate ligands resulting in a six-coordinate complex. The structure consists of Cd(H2O) and Cd(H2O)2 units bridged by SCN- and 3-pyc- ligands, thus forming a 3D coordination polymer (Figs. 1, 2). The
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carboxylate moieties of the 3-pyc- ligands act both as bidentate and bridging groups (totally tridentate) in a l-1,3 mode, where two oxygen atoms of the carboxylate group are bidentate toward the Cd(II) ion to create a 4-membered chelate ring. Parallel chains are now bridged via the N- and O-atoms of all 3-pyc- ligands. The SCN- anions doubly bridge each two Cd(II) ions via the N- and S-atoms. The dimeric units are grown into a 3D framework through the bridging by the 3-pyc- and SCN- anions. The CdCd distances within the [Cd2(3-pyc)2] ˚ ; and, the intrachain CdCd distances moieties are 8.148(2) A ˚. within the [Cd(SCN)]n chains are 6.400(2) A Cd3OSO4 nano-particles can be synthesized by the decomposition of the precursor 1 using oleic acid as a surfactant in air. The morphology and size of the prepared Cd3OSO4 was further investigated using SEM. The thermolysis of 1 produces a regular shape for the Cd3OSO4 nanoparticles at 280 °C and 300 °C (Fig. 3). The final product decomposition of 1, based on their XRD patterns (Fig. 4), is orthorhombic Cd3OSO4. The phase purity of the nanoparticles is obvious since all the diffraction peaks are perfectly indexed to orthorhombic Cd3OSO4 with lattice parameters ˚ , b = 23.343 A ˚ , c = 6.853 A ˚ , Z = 8 and a = 6.976 A S.G. = Cm2a, which are identical to those in the JCPDS card file no. 25-0113. To the best of our knowledge, this is the first report of a synthesis of nano-sized Cd3OSO4 by the direct thermolysis of a coordination polymer.
4 Conclusions A new Cd(II) three-coordination polymer, {[Cd3(3-pyc)4 (NCS)2(H2O)4]2H2O}n; 3-Hpyc = 3-pyridinecarboxylic acid}, has been synthesized using a thermal gradient approach.
Fig. 4 XRD pattern Cd3OSO4 prepared after thermolysis of 1 under special condition
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Compound 1 was structurally characterized by singlecrystal X-ray diffraction and consists of a 3D coordination polymer. This polymer precursor has been thermally decomposed in a suitable surfactant to obtain nano-sized Cd3OSO4. To the best of our knowledge, this is the first report of a synthesis of nano-sized Cd3OSO4 by this type of coordination polymer. This shows that coordination polymers may be suitable precursors for the preparation of desired nanoscale materials.
5 Supplementary Material The crystallographic data (excluding structure factors) for compound 1 has been deposited with the Cambridge Crystallographic Data Centre (CCDC) as supplementary publication number CCDC-758891. Acknowledgment University.
This work was supported by Tabriz Azad
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